Thanks for all that Baracus, very interesting (and the use of my pic there, did you know the one you've posted is cropped?) Some comments.
I'd be happier if you used something that bolted to the patibulum rather than just screwed in like those hooks, they aren't all that robust and really aren't intended for bearing that much weight. See what your local hardware store has in terms of fittings. You could also try a good solid screw fixed to the top of the patibulum, which you could hook things over, it will take more stress.
As for the wood, there are two things to consider. First, is it strong enough? I think the wood you have there is, particularly if it is fixed to your door frame and not standing by itself. Second, does it look good? This is where larger/thicker beams come in, to give that aesthetic touch. It looks like your timber is deep enough for the job, but it would look better with something wider.
Then yes you need to work on your foot fixing, whether a footrest or a loop of some kind that you can hook your feet into. Ultimately you want to be able to get the effect of full suspension, where the weight is distributed across arms and shoulders and legs, not largely supported by your feet. That's when you will get that enhancement of the upper body and arms, that stress that looks so beautiful in properly done crux.
On this last note, first and foremost keep safety in mind. Any self crux fittings you have must hold you securely, yet be easy to get out of! That's why a loop for the feet, something you can step out of, is better than full bindings. Look at some of Makar's foot binding for ideas here. Our old friend Batman even had a cross with a pair of old shoes nailed to it, which he could slip his feet in and out of.
Think about what you are after. Personal experience, appearance, usefulness for photo manips? Ugly bindings can be photoshopped out, much harder to get the effect of actual suspended crux!
It is hard when you have limited space, as you seem to have, camera angles can be a problem, but don't give up, I'm interested to see what you can achieve and whether I might even be able to use some
Just remember, have fun and please yourself first, all else will follow.
I like it